
## Load Fcount output from : DEXSeq_after_Fcount.R into DEXSeq
## Copyright 2015 Vivek Bhardwaj (bhardwaj@ie-freiburg.mpg.de). Licence: GPLv3.

suppressPackageStartupMessages({
  require(DEXSeq)
})

## Read Fcount output and convert to dxd
DEXSeqDataSetFromFeatureCounts <- function (countfile, sampleData, 
                                            design = ~sample + exon + condition:exon, flattenedfile = NULL) 

  {
        # Take a fcount file and convert it to dcounts for dexseq
        message("Reading and adding Exon IDs for DEXSeq")
        read.table(countfile,skip = 2) %>% dplyr::arrange(V1,V3,V4) %>% dplyr::select(-(V2:V6)) -> dcounts
        colnames(dcounts) <- c("GeneID", rownames(sampleData) )
        id <- as.character(dcounts[,1])
        n <- id
        split(n,id) <- lapply(split(n ,id), seq_along )
        rownames(dcounts) <- sprintf("%s%s%03.f",id,":E",as.numeric(n))
        dcounts <- dcounts[,2:ncol(dcounts)]
        
        dcounts <- dcounts[substr(rownames(dcounts), 1, 1) != "_", ] #remove _ from beginnning of gene name 
        
        ## get genes and exon names out
        splitted <- strsplit(rownames(dcounts), ":")
        exons <- sapply(splitted, "[[", 2)
        genesrle <- sapply(splitted, "[[", 1)
        
        ## parse the flattened file
        if (!is.null(flattenedfile)) {
                aggregates <- read.delim(flattenedfile, stringsAsFactors = FALSE, 
                                         header = FALSE)
                colnames(aggregates) <- c("chr", "source", "class", "start", 
                                          "end", "ex", "strand", "ex2", "attr")
                aggregates$strand <- gsub("\\.", "*", aggregates$strand)
                aggregates <- aggregates[which(aggregates$class == "exon"), # exonic_part
                                         ]
                aggregates$attr <- gsub("\"|=|;", "", aggregates$attr)
                aggregates$gene_id <- sub(".*gene_id\\s(\\S+).*", "\\1", 
                                          aggregates$attr)
                # trim the gene_ids to 255 chars in order to match with featurecounts
                longIDs <- sum(nchar(unique(aggregates$gene_id)) > 255)
                warning(paste0(longIDs, 
                               " aggregate geneIDs were found truncated in featureCounts output"), 
                        call. = FALSE)
                aggregates$gene_id <- substr(aggregates$gene_id,1,255)
                
                transcripts <- gsub(".*transcripts\\s(\\S+).*", "\\1", 
                                    aggregates$attr)
                transcripts <- strsplit(transcripts, "\\+")
                exonids <- gsub(".*exon_number\\s(\\S+).*", "\\1", # exonic_part_number
                                aggregates$attr)
                exoninfo <- GRanges(as.character(aggregates$chr), IRanges(start = aggregates$start, 
                                                                          end = aggregates$end), strand = aggregates$strand)
                names(exoninfo) <- paste(aggregates$gene_id, exonids, 
                                         sep = ":E")
                
                names(transcripts) <- names(exoninfo) 
                if (!all(rownames(dcounts) %in% names(exoninfo))) {
                        stop("Count files do not correspond to the flattened annotation file")
                }
                matching <- match(rownames(dcounts), names(exoninfo))
                stopifnot(all(names(exoninfo[matching]) == rownames(dcounts)))
                stopifnot(all(names(transcripts[matching]) == rownames(dcounts)))
                dxd <- DEXSeqDataSet(dcounts, sampleData, design, exons, 
                                     genesrle, exoninfo[matching], transcripts[matching])
                return(dxd)
        }
        else {
                dxd <- DEXSeqDataSet(dcounts, sampleData, design, exons, 
                                     genesrle)
                return(dxd)
        }
  
}

